doc/technical/fd-management.txt

   1 Overview of the filedescriptor subsystem
   2 Adrian Chadd <adrian@creative.net.au>
   3
   4 $Id: fd-management.txt 6 2005-09-10 01:02:21Z nenolod $
   5
   6
   7 Filedescriptor lists
   8 --------------------
   9
  10 The filedescriptor list is managed through the routines in fdlist.c .
  11 These include:
  12
  13 fd_open() - tag an FD as "open" and active
  14 fd_close() - tag an FD as "closed" and close() the filedescriptor
  15 fd_note() - update the filedescriptor tag
  16
  17 You can get the current list of open filedescriptors through /stats F as
  18 an oper.
  19
  20
  21
  22 FD lists
  23 --------
  24
  25 The FD list support is very alpha. There are a few lists defined:
  26
  27 typedef enum fdlist_t {
  28     FDLIST_NONE,
  29     FDLIST_SERVICE,
  30     FDLIST_SERVER,
  31     FDLIST_IDLECLIENT,
  32     FDLIST_BUSYCLIENT,
  33     FDLIST_MAX
  34 } fdlist_t;
  35
  36 FDLIST_NONE             Not on any list (ie close()d)
  37 FDLIST_SERVICE          A service - listen() sockets, resolver, etc
  38 FDLIST_SERVER           Server connections
  39 FDLIST_IDLECLIENT       An idle client
  40 FDLIST_BUSYCLIENT       A busy client
  41 FDLIST_MAX              Used for bounds checking
  42
  43 The idea is that the SERVICE sockets need polling frequently, the SERVER
  44 sockets also need polling frequently, BUSYCLIENT is for busy clients
  45 which need frequent polling (eg we're trying to write to them), and
  46 IDLECLIENT is for clients which we don't need to poll frequently.
  47 THIS hasn't been decided upon yet.
  48
  49
  50
  51 File operations
  52 ---------------
  53
  54 The file operations are also wrapped through file_open() and file_close()
  55 which handle calling fd_open() / fd_close() and tracking the filedescriptors
  56 correctly. fbopen() / fbclose() use file_open() / file_close() too.
  57
  58 fileio.c defines the functions:
  59
  60 int
  61 file_open(const char *filename, int mode, int fmode)
  62
  63 A wrapper around open(filename, flags, mode). Read the open manpage for
  64 information. file_open() enforces filedescriptor limits and tags the FD
  65 through fd_open().
  66
  67 void
  68 file_close(int fd)
  69
  70 A wrapper around close() for files. close() handles fd_close()ing the fd.
  71
  72
  73 FBFILE *
  74 fbopen(const char *filename, const char *mode)
  75
  76 void
  77 fbclose(FBFILE *fb)
  78
  79 These are the 'buffered disk IO' routines. You can read the code yourself.
  80 Note that these routines use file_open() and file_close().
  81